Mechanism of Relaxant Action of Ethyl 6-amino-5-cyano-2-methyl- 4-(pyridin-4-yl)-4H-pyran-3-carboxylate Mainly Through Calcium Channel Blockade in Isolated Rat Trachea.

ABSTRACT

This study aims to investigate the mechanism of relaxant action of Ethyl 6-amino-5-cyano-2-methyl-4-(pyridin- 4-yl)- 4H-pyran-3-carboxylate (1) in in silico study and ex vivo tracheal rat rings pre-contracted with carbachol (1 µM). Compound 1 was more active than theophylline [a phosphodiesterases (PDE’s) inhibitor] used as positive control. Moreover, pretreatment with 1 significantly shifted to the right the carbachol-induced contraction and did not allow to reach the maximum effect (p< 0.001). In addition, compound 1 (96.30 µM) produces significant (100%) relaxant effect on the contraction induced by KCl (80mM), and the CaCl2-induced contraction was completely abolished by 1 as nifedipine does (a L-type calcium channel blocker), used as positive control (p< 0.001). Meanwhile, in the presence of isoproterenol (a β-adrenergic agonist), propranolol (a β-adrenergic antagonist), and K+ channel blocker 2-AP the relaxant curve was significantly modified (p< 0.05). Compound 1 was docked on an outer cavity located on the intracellular side of the human L-type calcium channel model and interacts in the following chains and residues chain IP (G51, W52, T53, D54), IVP (R45, E50, A51, Q53, D54) and IS6 (W4, F7). In conclusion, ex vivo and in silico approaches suggest that compound 1 induces its relaxant effect mainly by calcium channel blockade, but other mechanisms like potassium channel and cAMP accumulation could be involved.